There are many methods and apparatus for measuring height. The simplest one among them may be to directly measure the height by means of a ruler. With the development of science and technology, a great variety of advanced height measurement instruments have been developed. It is observed that the advance heads toward digitalized measurements, which are rapid, convenient and more accurate. For example, the conventional ultrasound height measurement instruments measure the height utilizing the time difference between transmission of an ultrasound wave and reception of the echo of the ultrasound wave reflected when directed onto the object to be measured. However, when using such an ultrasound height measurement instrument to measure height, the ultrasound transmitter or the object that reflects the ultrasound wave needs to be placed on the head of the measured object. Therefore, these height measurement instruments have to contact the measured object, which causes great inconvenience to the measurement.